Safety guard



Nov. 18, 1958 J. A. BREADNVER 2,350,525

SAFETY GUARD Filed July 6, 1953 2 sheets-sheet 1 IN VEN TOR. Ei} Jae/f A. ,Brazdner- BY M NOV. 18, 1958 BREADNER 2,860,525

' SAFETY GUARD Filed July 6, 1953 2 Sheets-Sheet 2 IN VEN TOR. 140% A. B rmdner fiarney.

a wza/x wr n s MI United States Patent SAFETY GUARD Jack A. Breadner, Ottawa, Ontario, Canada Application July 6, 1953, Serial No. 366,266

1 Claim. (Cl. 74-613) dangerous machinery in this class. Various devices have been designed for protecting the operators of such machines against injury. The prior devices generally consist of some sort of mechanical guard operated in timed relation to the operation of the descending element of the machine. The guards have been more or less unsatisfactory in that they are bulky and costly, hamper production and constitute a sourceof constant annoyance to the operators. Frequently such guards provide no protection if a mechanical failure occurs permitting the descending element to fall prematurely. H

It is an object of this invention to provide a simple, inexpensive and effective safety device for drop hammers, presses and like machines.

It is another object 'of this invention to provide a positive safety guard which will warn the operator regardless of the operation of the machine and especially in case of any mechanical failure which permits the descending element to fall prematurely.

It is a further object of the invention to provide a safety device for a drop hammer or press which functions with a minimum of annoyance and inconvenience to the operator of the machine.

The invention will be described with reference to the accompanying drawings, in which,

Figure l is a left side elevation view of a bench press to which the safety device has been attached,

Figure 2 is a front elevation view of the bench press shown in Figure 1, a

Figure 3 is a right side elevation view of the bench press shown in Figure 1,

Figure 4 is a plan view of the safety arm indicating its sweep,

Figure 5 is a schematic diagram of the switch circuits controlling the safety device,

Figure 6 is an elevation view of the safety arm actuating means,

Figure 7 is an elevation view of another embodiment of the safety arm actuating means,

Figure 8 is a front elevation view of a drop hammer with the safety device installed thereon, and

Figure 9 is a side elevation of the drop hammer shown in Figure 8.

Referring to Figures 1, 2 and 3 of the drawings the invention is shown associated with a bench press of well known construction and having a base 1, a frame 2 Patented Nov. 18, 1958 and a ram 3. The flame 2, adjustably mounted on the base 1, consists of two side members 4 and 5 which terminate in a table 6. The other ends of the side members support a drive shaft 7 on which is eccentrically mounted (between the side members) a descending element comprising a crank or connecting rod 8 carrying by means of a wrist pin 8a the ram 3 which supports a die 3a. A flywheel 9 drivingly connected to a motor 10 is mounted on one end of the shaft 7. A tripping lever 11 operates a clutch 12 in the flywheel 9 to set the press in motion and thus cause the ram to descend and strike a work piece on the table 6, all in the conventional manner.

A switch A mounted on the side member 5 is operated by the tripping lever 11. A second switch B carried by a plate 13 is mounted on the side members 4 and 5 byscrews 14 and is arranged to be operated by rotation of the crank 8 and consequent downward movement of the ram or press mechanism 3. e

As shown in Figures 1, 2 and 3, a supporting plate 15 is mounted in any convenient position on one of the side members 4 or 5 by means of screws or the like 16. As more fully shown in Figure 6, an actuating means such as a solenoid 17 is fixed to a plate 15 and has a piston plunger 18 and a return spring 19. A rod 20 mounted on the plunger 18 is pivotally connected toa link 21. A' lever 22 rotatably supported in a bearing 23 is'pivotally connected to the link 21 and carries a sweeping arm 24, which is adjustably mounted thereon, as for example, by a set screw or the like 25. An adjusting screw 26 and a lock nut 27 connecting the plunger 18 and the supporting plate 15 provides another means of adjustment between the plunger and the sweeping arm. The solenoid is connected by wires 28 to any suitable source of E. M. F. through switches A and B as shown diagramatically in Figure 5.

Another form of actuating means is shown in Figure 7 wherein the piston plunger 18 with its return spring 19 is operated by a hydraulic cylinder'29. I

Figures 8 and 9 of the drawings illustrate the invention as installed on a drop hammer, also of well known construction. The drop hammer has a base 30 a portion of which constitutes a table 31. Two side members 32 which extend from the base 30 carry at their upper ends a drive shaft 33 mounted in bearings 34. A pulley 35 is mounted on the shaft 33 between the members 32 and is connected by a strap or belt 36 to a hammer or striking element 37 by means of a clevis 38. A shaft 39 having a driving pulley 40 on one end, a crank 41 on the opposite end and a gearing 42 intermediate the ends thereof is mounted on the members 32 above the table 31. A rod 43 connects the crank 41 to an arm 44 which is attached to one end of a belt 45. The other end of the belt 45 is fastened to a pulley 46 which is mounted on one end of the drive shaft 33. A tripping lever 47 controls the operation of the machine and permits the hammer 37 to strike a work piece on the table 31, also all in the conventional manner.

The switch A is located on one of the side members 32 adjacent the tripping device 47 and is operable thereby. The switch B is connected to a bracket 48 which is adjustably mounted by means of set screw 49 on a rod 50 fixed to one of the side members 32. Switch B is closed by engagement therewith of a laterally projecting portion 37a of the hammer 37 during its downward movement.

In operation of the bench press with the safety device in accordance with the invention a piece of material to be pressed is placed on the table 6 and lever 11 is tripped which sets the press mechanism in motion causing the ram or press to drop rapidly and strike the material on the table. With operation of lever 11 switch A is closed causing the solenoid 17 or the hydraulic cylinder 29 to move the piston plunger 18 and in turn actuate the rod 20, link 21 and lever 22" to swing the arm 24 across the table 6, that is, to swing the arm 24 from the full line position to the dotted line position as shown in Figure 4. The movement of the arm will give the necessary warning to the operator and in fact will sweep his hands clear if they are not already clear of the ram. The spring 19 will return the actuating means to its normal position when the ram is returned to its original starting position. If for any reason the. clutch or the operating mechanism of the press should be released without the operation of the tripping lever 11 any downward movement of the ram will cause switch B to be closed thus operating the safety mechanism as described above. Switch B will remain closed until the ram returns to its original starting position at which time the sweeping arm returns to its normal position. Thus it will be observed that the danger zone is guarded by the arm 24 during the complete downward and return movement of the ram. Consequently switch B, a'safety and holding switch, insures operation of the safety mechanism in case of any mechanical failure in the pressing machine which permits the ram to drop.

The operation of the drop hammer and the safety device as shown in Figures 8 and 9 is similar to that de scribed above. Switch A is closed by tripping of the lever 47 thus closing the circuit shown in Figure which causes operation of the safety device. In this embodiment switch B is adjustably mounted on the rod 50 and is closed by portion 37a on the hammer 37 when it is released. It will be noted that any downward movement of the hammer 37 will set the safety mechanism in motion thus protecting the operator whether the drop hammer be set in motion by the normal tripping lever or because of some mechanical failure in the machine.

It will be apparent that switch B may be mounted on the press in a position similar to that shown on the drop hammer or vice versa. It will also be apparent that the piston plunger 18 may be operated equally well whether a solenoid 17 or a hydraulic cylinder 29 is used to supply the motive power for operating the sweeping arm 24.

It will be seen that the safety device herein described may be readily and inexpensively installed on any machine having a descending element and in which the operator has occasion to place his hands in the path thereof without any change in construction of the machine. It will also be observed that the present invention provides a simple and efiicient safety device which in no way annoys or hampers the operator and at the same time provides absolute protection under all circumstances.

I claim:

In a safety device for power presses and like machines, the combination with a frame having a work table, a descending element mounted on said frame arranged to strike a piece of work on said table, driving means for the descending element, and a tripping lever, a switch mounted on the frame adjacent the descending element and solely actuatable by each and every descending stroke of said element, a second switch mounted on the frame adjacent the tripping lever and operable thereby, a sweeping arm pivotally mounted in the frame for sweeping the area above said table, a linkage connected to said arm to swing the latter, and power means operating the linkage in response to each and every actuation of either of said switches.

References Cited in the file of this patent UNITED STATES PATENTS 851,909 Watkins Apr. 30, 1907 1,041,092 Jones Oct. 15, 1912 1,078,391 Wallbillick Nov. 11, 1913 1,166,981 Graham Jan. 4, 1916 1,167,611 Aliano Jan. 11, 1916 1,370,369 Schofield Mar. 1, 1921 1,394,501 Parkinson Oct. 18, 1921 1,405,466 Van Horn Feb. 7, 1922 1,444,336 Maecker Feb. 6, 1923 2,082,210 McMaster June 1, 1937 2,683,515 Horn July 13, 1954 2,724,287 Knoth Nov. 22, 1955 FOREIGN PATENTS 687,115 Germany Jan. 23, 1940 

